Acta Polytechnica CTU Proceedings 5:17–21, 2016
doi:10.14311/APP.2016.5.0017
© Czech Technical University in Prague, 2016
available online at http://ojs.cvut.cz/ojs/index.php/app
DESIGN PARAMETERS OF BUFFER STOPS
Petr Guziur
Brno University of Technology, Faculty of civil engineering, Veveří 331/95, 602 00 Brno
correspondence: guziur.p@fce.vutbr.cz
Abstract. Paper discuses reasons of building buffer stops and situations that may occur in railway
station leading to build safety tracks. Also discusses parameters of buffer stops that enter its design,
such as collision speed and kinetic energy absorbing capacity. Furthermore, presents categories of
buffer stops depending on principles of absorbing the kinetic energy and points pros and cons of each
structure.
Keywords: Buffer stop, kinetic energy, braking force, dead-end track.
1. Introduction
Buffer stop is a device at the end of dead-end track or
closed track with a purpose to stop the rolling stock.
In Czech Republic it is allowed to use three types
of buffer stops (according to national regulation ČD
Ž9 [1]). All three types are fixed (rigid) construction,
yet there are numerous designs of buffer stops used
abroad. We can divide buffer stops in categories
depending on the principles of absorbing the kinetic
energy, which is the most important parameter of
buffer stops. As basic categories we can name fixed
buffer stops, hydraulic buffer stops and friction buffer
stops. Every type has its pros and cons and suitable
place to be installed (depending on circumstances).
1.1. Flank Protection
One of the places, where buffer stop has to be installed,
is the end of safety track which represents direct flank
protection of train paths. There are two types of flank
protection of train path:
• direct flank protection – protection of rolling stock
from non-permitted ride of rolling stock from side
approaching track – flank protection switch or derail
is used,
• indirect flank protection – protection of rolling stock
from non-permitted ride of rolling stock from side
approaching track – signals with prohibiting signal
is used.
And there are different conditions for flank protection of train path with speed up to 120 km.h−1 and
above this speed. Direct flank protection of train path
with speed higher 120 km.h−1 is required:
• from all sidings,
• from all service tracks.
In this case, rolling stock arriving from siding or
service track should head to the safety track and
probably has low speed at its end (by the buffer stop).
Another situation with possibility of higher impact
speeds may occur on safety tracks from running tracks
(see chapter 1.1.1).
1.1.1. Mutually Excluded Train Path
Amongst other conditions, safety and signalling plant
of second or higher category has to forbid the simultaneous setting of train path for which the train path
with higher speed than 120 km.h−1 meets, crosses
or overlaps with continuation of another train path.
This condition is crucial for direct flank protection. If
there is no direct flank protection of the train path
with speed higher than 120 km.h−1 , one of train paths
is not allowed to be set or the speed is restricted up
to 120 km.h−1 . Speed restriction depends on possibilities of main signals (what speed can be signalled).
In railway station, where restricted speed is used, the
restriction brings speed to lower level, than in railway
station, where no restriction is needed (with speed of
120 km.h−1 ). This issue causes regular delay of trains
on daily bases, since not even system like KANGO is
able to cope with this situation. The only result is to
build flank protection switches not only from sidings
and service tracks but even from running tracks where
threat of the train path with speed higher than 120
km.h−1 occurs.
2. Buffer Stop’s Design
Parameters
As a crucial parameter for designing buffer stop is
its kinetic energy absorbing capacity, thus stopping a
rolling stock of certain mass with a certain collision
speed. There are various situations of buffer stop’s
location, therefore it is needed to approach the design
individually. Whether the buffer stop is at the end
of a dead-end track in station by platform, or ends
a safety track (either from sidings, service track or
even running tracks). Each situation gives us different
speed and different type of train (its mass) that can
run into a buffer stop. As mentioned above, amount
of kinetic energy that buffer stop is able to absorb is
the crucial parameter for its design. Kinetic energy
of moving rolling stock can be calculated as sum of
the kinetic energy of transitional motion and kinetic
energy of rotating parts of the rolling stock (1.).
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Acta Polytechnica CTU Proceedings
Petr Guziur
Vehicle groups
Trains
Cars
Locomotives
Vehycle types
Regular passengers or freight trains
Electric motor unit
Cars with mechanical traction transition
Cars with traction motors
Passengers cars
Full freight cars
Empty freight cars
Steam
Electric
Motor
ρ[-]
0,06
0,15 - 0,20
0,12 - 0,15
0,20 - 0,025
0,04 - 0,06
0,04 - 0,05
0,1 - 0,12
0,08 - 0,10
0,20 - 0,30
0,15 - 0,30
Table 1. Coefficient of rotating parts [2]
Speed [km.h−1 ] Speed [m.s−1 ]
10
15
2,78
4,17
100
386
869
Impact
200 300 400 500
773 1159 1546 1932
1739 2608 3478 4347
mass [t]
600 700 800 900 1000
2319 2705 3091 3478 3864
5217 6086 6956 7825 8694
Table 2. Examples of kinetic energy [kJ]
(1.)
• Ekin,c ... total kinetic energy [J];
Ekin,c = Ekin,p + Ekin,r
(2.)
Ekin,p =
1
mv 2
2
(3.)
1 2
Iω
2
With substitution equation (2.) and (3.) into equation (1.) and following modification it is possible
to calculate kinetic energy of moving rolling stock,
using equation (4.).
Ekin,r =
(4.)
Ekin,c =
1
m(1 + ρ)v 2
2
• Ekin,c ... total kinetic energy [J];
• k ... safety coefficient [-].
In Table 3 are shown examples of safety coefficient
graded by the level of protection and type of train
according to Austrian standards [3].
2.1. Collision Speed
The collision speed is defined as the maximum permissible speed in which trains may travel when colliding
with buffer stop. There are various approaches, how
to determine collision speed. German standard DS
800 01 [4] use the collision speed based on train type:
• passengers trains: 15 km.h−1
• freight trains: 10 km.h−1
• Ekin,p ... kinetic energy of transitional motion [J];
Austrian standard DV B 53 [3] use the collision speed
based on track type:
• Ekin,r ... kinetic energy of rotating parts [J];
• main line trains: 15 km.h−1
• m ... weight of rolling stock [kg];
• empty passengers trains or shunting: 10 km.h−1
• v ... collision speed [m.s−1 ];
Take an example how the collision speed can be calculated. Driver is responsible to make a proper braking
according to signals. By error he overlooks a presignal and has no information about decelerating the
train. He starts to decelerate at the point of signal
with prohibiting signal using the emergency brake.
Table 4 displays braking distances (using operating
brakes and emergency brake) and speeds of trains at
the end of dead-end track (model situation: assuming
the distance between signal with prohibiting signal
and buffer stop is 100 m).
Parameters for Table 4:
• I ... moment if inertia [kg.m2 ];
• ω ... angular speed [s−1 ];
• ρ ... coefficient of rotating parts [-].
Examples of kinetic energy are given in Table 2
For buffer stop, as a device (structure) that has to
work properly and must ensure high level of safety
and reliability, we need to involve a safety coefficient
in calculations. Therefore, the buffer stop’s kinetic
energy absorbing capacity has to be determined as
follows:
• * train will stop before the buffer stop,
R >= Ekin,c k
• Os deceleration – 0,50 m.s−2 (2x unit 451/452) [5],
• R ... buffer stop’s kinetic energy absorbing capacity
• R, Ex, IC deceleration – 0,45 m.s−2 (locomotive
[J];
18
363 + 8 cars type Y) [5],
vol. 5/2016
Design Parameters of Buffer Stops
Type of train and security level
Passengers trains
Freight trains and shunting
Freight trains and shunting, when it is necessary to
protect various systems which are located behand or
nearby buffer stop
Freight trains and shunting, in cases where there are
traffic zones, structures or residential houses located
behind or nearby buffer stop
Preventing the fall of any train or rolling stock into abyss
k [-]
1,5
1,2
1,5
1,8
2,0
Table 3. Safety coefficient [3]
Speed
[km.h−1 ]
50
60
70
80
90
100
Braking distance [m]
Os
192,90
277,78
378,09
493,83
625,00
771
R, Ex, IC
214,33
308,64
420,10
548,70
694,44
857,34
Emergency braking
40,19
57,87
78,77
102,88
130,21
160,75
Speed at the end of dead-end track
[km.h−1 ]
Os R, Ex, IC
Emergency brake
35
37
*
48
49
*
60
61
*
71
72
13
82
83
43
93
94
61
Table 4. Deceleration of trains
Buffer
Stop
Type
Rail
buffer
stop
Concrete type
"SUDOP"
Concrete type
"DSB"
6 cars of
15 t
1,0 km.h− 1
1 car of
80 t
1,6 km.h− 1
0,7 km.h− 1
1,1 km.h− 1
1,0 km.h− 1
1,6 km.h− 1
Table 5. Resistances of buffer stops used in Czech
Republic [1]
Figure 1. Example of hydraulic buffer stop (Oleo
comp.) [7]
• emergency brake deceleration – 2,40 m.s−2 .
is unacceptable (see Table 6).
3. Types of Buffer Stops
3.1. Fixed buffer stops with mechanical
bumpers
Fixed (rigid) buffer stop is one of the most used types
of buffer stops considering its history as an oldest one.
Construction of fixed buffer stop consists of a block
or frame fixed rigidly to the rails or the ground. As
other constructions, fixed buffer stop has its pros and
cons. One of advantages is that it can be placed at
the end of the dead-end track, thus it does not reduce
the usable length of the track. However, in this case
cons prevail, such as low resistance and manner of
deceleration. Resistances (as a state of usability) of
fixed buffer stops used in Czech Republic are shown
in Table 5.
If the mass or speed is higher, either the buffer
stop or the train is destroyed. Assuming both buffer
stop and rolling stock frame will be reinforced significantly, and therefore cannot deform, the deceleration
3.2. Hydraulic Buffer Stop (Fixed
Buffer Stop with Hydraulic
Bumpers)
Hydraulic buffer stops are similar in construction to
fixed. Consist of a block or frame fixed rigidly to
the rails or the ground. Hydraulic buffer stops absorb
kinetic energy in gradual manner (depends on the type
of the hydraulic bumpers). If the energy is higher than
the bumper is able to absorb, buffer stop is destroyed.
PARAMETERS of the buffer stop on Figure 1:
• kinetic energy absorbing capacity: 2688 kJ,
• bumpers stroke: 2400 mm.
3.3. Friction Buffer Stop
Friction buffer stop is the most effective way to stop
moving rolling stock. The way of absorbing the kinetic
energy, thus decelerating the rolling stock is the most
efficient and safe. Not only the train decelerates in
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Acta Polytechnica CTU Proceedings
Petr Guziur
Impact speed
[km.h−1 ]
Impact speed
[m.s−1 ]
5
10
15
1,39
2,78
4,17
Stroke of mechanical bumpers [mm] [6]
75
105
Decelartion
Overload Decelartion
Overload
[m.s−2 ]
[m.s−2 ]
6,43
0,66g
4,59
0,47g
25,72
2,62g
18,37
1,87g
57,87
5,90g
41,34
4,21g
Table 6. Deceleration of train and overload on passengers on impact the fixed buffer stop
Figure 2. Length needed for buffer stop placement
and to ensure braking distance [8]
gradual manner over a longer distance (time period),
but the kinetic energy absorbing capacity could be
very high. Friction buffer stop generally consist of
rigid steel frame with buffers, connected to rails using
arresting devices (friction jaws). In case of collision,
kinetic energy is transformed into heat by means of
friction. Therefore, energy absorbing capacity of friction buffer stop depends on the number of friction
jaws, friction coefficient resp. braking force of jaws
and length of braking. Nevertheless, there is a disadvantage. Friction buffer stop needs a braking distance,
therefore cannot be placed at the end of the deadend track and shortens its usable length. Moreover
the track behind the buffer stop needs to be horizontally straight and contain no welds and joints or other
obstacles over rails.
NOTES for Figure 2:
• LV ... length needed for buffer stop placement and
to ensure braking distance;
• LB ... buffer stop length;
• LW ... maximum braking distance.
Three types of friction buffer stops can be named:
• friction buffer stop (without additional brakes), see
Figure 3;
• friction buffer stop with additional brakes, see Fig-
ure 4;
• friction buffer stop with hydraulic bumpers
(with/without additional brakes).
NOTES for Figure 3:
(1.) Collision triangle;
(2.) Breaking devices;
(3.) Buffers;
Figure 3. Friction buffer stop without additional
brakes [8]
Figure 4.
brakes [8]
(6.) Reinforcement.
NOTES for Figure 4:
(1.) Additional arresting devices for added braking;
(2.) Steel profile below rails for reinforcement of the
track;
(3.) Jointed connection belts between arresting de-
vices;
(4.) Lateral connection between arresting devices.
3.3.1. Braking force
Braking force is the determining factor of friction
buffer stop. As mentioned above, buffer stop must
absorb high amount of kinetic energy. Calculation of
breaking force in case of friction buffer stops depends
on numbers of arresting devices, braking force of each
arresting device and maximum braking distance.
(4.) Device for returning the buffer stop to working
position after collision;
(5.) Reinforcement;
20
Friction buffer stop with additional
R = nb Fb LW
• R ... buffer stop’s kinetic energy absorbing capacity
[J];
vol. 5/2016
Design Parameters of Buffer Stops
Figure 5. RAWIE 16 ZEB, stopping distance/impact
speed/impactmass diagram, safety coefficient 1,0 and
1,5 [9]
etc. In general, three types of buffer stops are used,
depending of the principle of absorbing the energy.
Fixed buffer stops are more than useless for higher
collision speeds considering its manner of deceleration
and its resistances. However, using fixed buffer stops
is justified e.g. in shunting yards, where are low speeds
and no passengers on board. As more appropriate
ending of dead-end track is usage of hydraulic or friction buffer stop. Resistances of those types are much
higher than fixed buffer stops. Both this construction
decelerates train in gradual manner and no harm to
the rolling stock or buffer stop itself is done if the
design was precise.
Acknowledgements
• nb ... number of arresting devices [-];
• Fb ... braking force of a single arresting device [N];
• LW ... maximum braking distance [m].
Braking force of friction buffer stop with additional
brakes comes from formula up there. Formula is modified considering braking force of additional brakes
while braking distance of each additional arresting
device is included separately.
R=
nZ
X
2Fbi LW i
i=1
• R ... buffer stop’s kinetic energy absorbing capacity
[J];
• nZ ... number of a pair of additional arresting
devices [-];
• Fbi ... braking force of a single arresting device,
based on a braking distance [N];
• LW i ... length of braking distance of a pair of
arresting devices [m].
An example of friction buffer stop’s braking effectiveness is shown in Figure 5 (friction buffer stop
without additional brakes with absorbing capacity of
640 kJ.m−1 ).
4. Conclusion
Many aspects have to be taken in account while designing buffer stop. One has to consider its location
– ending of dead-end track in railway station, ending
safety track from sidings, service track or running
track. Every scenario brings different requirements
such as type of train, collision speed, impact mass
The paper was created with support of the project no.
LO1408 "AdMaS UP - Advanced Materials, Structures
and Technologies" supported by the Ministry of education,
youth and sports within the targeted support of program
"National program for sustainability I".
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